Lindsay Lohan has blamed loneliness, "sycophants and bad influences" for her troubles.
The 26-year-old former child star is trying to salvage her acting career after being arrested six times, spending time in prison and five trips to rehab.
Lindsay told Us Weekly magazine: "Kids go through ups and downs, try cigarettes, drugs and drinking. It's human nature.
"It took a while but it's like, What was I thinking? Why did I allow so many sycophants and bad influences to be around me? I was lonely and I didn't realise it.
"That's why I came back home to New York. I never feel lonely there. I can see my family and I have really good people in my life."
The Mean Girls star also spoke about her relationship with ex-girlfriend, DJ Samantha Ronson, calling it "toxic".
Li-Lo said: "I was bold enough to say, 'Yeah, I like a girl. And?' That put her in a situation where she was being attacked every day. That's not fair. And what am I left with? Heartbreak. That was three years ago. It was my last serious relationship.
"I need to love myself first before I could be with anyone else, and I was going through a lot. Two toxic people cannot be together. End of story. We're friends now. That's how it started so I think that's how it was meant to be."
Lindsay is trying to turn her life around and is making her acting comeback playing Elizabeth Taylor in TV biopic Liz And Dick.
Asked what advice she would give her 16-year-old self, she said: "Don't drink and drive! And be careful who you surround yourself with."